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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | -3 |
| 4 | 28 |
| 5 | -110 |
| 6 | 1010 |
| 7 | -6636 |
| 8 | 67856 |
| 9 | -618120 |
| 10 | 7231048 |
| 11 | -82977400 |
| 12 | 1111357256 |
| 13 | -15222508080 |
| 14 | 231587495568 |
| 15 | -3664098311160 |
| 16 | 62674059676416 |
| 17 | -1120961847782976 |
| 18 | 21339716663592384 |
| 19 | -424956180060612864 |
[1,0,2,-3,28,-110,1010,-6636,67856,-618120, 7231048,-82977400,1111357256,-15222508080, 231587495568,-3664098311160,62674059676416, -1120961847782976,21339716663592384, -424956180060612864] |